Turn signal switch assemblies are well-known, and often include a self-cancelling mechanism carried by the steering wheel hub for engagement with an actuator on the turn signal switch assembly. The switch assembly is often rigidly mounted to the exterior of the steering column housing, although some switch cancellation assemblies are mounted interiorly of an exterior housing. However, the interior structures are generally more complicated so as to fit within the housing; and must be supplied as original equipment with the vehicles. In addition, access to such structures is obstructed, and thus substantially increases the labor, expense and time necessary to diagnose or repair problems in the turn signal and cancellation mechanism.
Externally mounted turn signal switch assemblies provide appreciable cost savings by simplicity in the original manufacturing and assembly, as well as in the case of repairing or replacing components of the switch assembly as shown in U.S. Pat. Nos. 4,013,850 and 3,809,833. Both of these patents disclose directional signal assemblies mounted to the steering column housing by a strapping clamp. In the self-cancelling turn signal system of U.S. Pat. No. 4,013,850, a pin rotates with the steering wheel hub so that it passes through a path intersecting a lever arm position on the exterior of the switch housing assembly. Unfortunately, the position of the switch housing along the axis of the steering column is dependent wholly upon the abilities of the installer to estimate a proper alignment and secure the strap clamp in the desired position. Accordingly, the cancellation pin may miss or make only partial contact with the lever. Misalignment may accelerate the wear of the contacting parts, or cause deformation or misalignment of the pin and lever contact point which interferes with proper operation of the turn signal or the cancellation mechanism.
In order to avoid arbitrary alignments of the switch housing with respect to the cancellation mechanism on the hub, attempts have been made to insert gauge blocks that position the lever at a fixed position relative to the rotatable hub that carries the cancellation pin. However, such alignment is extremely laborious and difficult since an operator who has secured a cancellation assembly in position on the hub must hold the switch housing while aligning the housing and also tightening the fastener to attach the switch housing to the steering column housing. Accordingly, an installer finds it difficult to hold and retain another item such as a gauge block between the relatively small surfaces between the hub and the switch housing, particularly where the housing must be properly positioned along an inclined axis of the steering column. In fact, use of alignment gauges would substantially increase the time for installation of the turn signal assembly, particularly if the housing may be initially secured to the steering column housing, then loosened to permit insertion of a gauge between the hub and the actuator. Such loosening or tightening to attempt alignment of the switch housing with respect to the cancellation mechanism carried on the hub can be extremely difficult due to the dashboard spacing, interior layout and other controls at the steering column. In addition, the cancellation pin is generally mounted diametrically away from the switch housing relative to the steering column and cannot contribute to alignment of the pin within the path of the exposed actuator. Moreover, unless the hub is also turned for alignment it would be extremely difficult for a single installer to position the cancellation pin toward the switch housing while holding the housing and tightening the fastener carried at an end of the strap clamp.